Method of transferring fluids through a permeable well lining

ABSTRACT

Fluid is transferred between surface facilities and a subsurface reservoir formation through a well, which is equipped with a well lining having a permeability of less than 50 Darcy and preferably a lower permeability than at least part of the reservoir formation in the vicinity of the well lining so that fluid transfer into or from the formation is equalized even if the formation comprises strata having different permeabilities.

BACKGROUND OF THE INVENTION

[0001] The invention relates to a method of transferring fluids througha permeable well lining.

[0002] Such a method is known from International patent applicationPCT/EP96/04887.

[0003] The well lining known from this prior art reference serves as asand/gravel screen and therefore has a sieve opening size, which issmaller than the size of the sand/gravel particles that are to beexcluded from the wellbore. However, this and other known sandscreenstypically only represent a limited flow restriction in order to avoidthat the influx of well effluents is inhibited. The permeability of thisand other conventional well screens is typically several thousands Darcyand is much higher than the permeability of the surrounding formationwhich may have a permeability which is less than 50 Darcy, or even aslow as 1 mDarcy in carbonate formations.

[0004] Therefore, the method according to the preamble of claim 1 oftransferring fluid between a reservoir formation and fluid processingfacilities at or near the earth surface via a well extending betweensaid formation and facilities, which well is equipped with a permeablewell lining, is known from International patent applicationPCT/EP96/04887.

[0005] A problem encountered with production of hydrocarbon fluids fromsubsurface reservoirs and with injection of steam, water or treatmentinto such reservoirs is that such reservoirs may be stratified and thatsome zones may have a significantly higher permeability than other zonesso that the transfer of fluid into or from the well is largelyconcentrated to the high permeability zones.

[0006] It is an object of the present invention to provide a method oftransferring fluids through a permeable well lining, which alleviatesthe problem of an unequal fluid transfer along the length of the lining,in particular if the well lining traverses stratified reservoir zoneshaving different permeabilities.

SUMMARY OF THE INVENTION

[0007] In the method according to the invention fluid is transferredbetween a subsurface formation and fluid processing facilities at theearth surface via a well, which is equipped with a well lining, whichhas a permeability which is lower than 50 Darcy.

[0008] Preferably the permeability of the well lining is lower than thepermeability of at least part of the subsurface formation in thevicinity of the well lining.

[0009] Preferably the well traverses several zones of a subsurfacehydrocarbon bearing reservoir formation, which zones have differentpermeabilities and the permeability of the well lining is selected lowerthan the permeability of the zone having the highest permeability whilstfractures or cavities will not be taken into account for determining thepermeability of the lining. If the permeability of the reservoir zonehaving the highest permeability is about 20 Darcy then the permeabilityof the well lining would be selected lower than 20 Darcy.

[0010] Suitably, the well lining is unfolded and/or expanded downholeand pressed against the wall of the wellbore or perforated productionliner and is made of a low permeable screen material such as a fabric,permeable rubber, a woven or sintered metal screen or a laser punchedmetal plate.

[0011] The well lining may be formed by an expandable hose or bladder,which is pressed against the wall of the wellbore either by mechanicalforce or by hydraulic pressure in case fluid is injected from the wellinto the formation. Alternatively, the well lining may be expanded byinflating a hose or bladder inside the lining or by expanding a slottedor perforated corrugated, cellular or foldable tubular within thelining.

[0012] The transferred fluid may be steam, acid, gel, surfactant, resin,a one or multiple component cement, or a treatment or stimulation fluid,which is pumped down from surface facilities through the well and welllining into the formation.

[0013] Alternatively, the fluid is a hydrocarbon fluid and/or water,which flows from the reservoir formation via the well lining and welltowards hydrocarbon fluid processing facilities at or near the earthsurface, whereas the produced water may be separated downhole from theproduced well fluid and be re-injected into a subsurface formation.

[0014] It is observed that International patent applicationPCT/EP99/03013 discloses a cellular well tube of which the cells may befilled with a one- or two-component cement slurry or treatment fluid,which is squeezed evenly into the surrounding formation or annulusthrough the outer wall of the cells, which wall may have a lowerpermeability than the surrounding formation. The fluid is pre-loaded inthese cells and the known method can therefore only be used to inject arelatively small volume of fluid evenly into the formation, which volumeequals that of the cells of the tube. The known method therefore is nota process where a significant amount of fluid is transferred via pumpingor otherwise during a prolonged period of time between surface fluidprocessing facilities and a subsurface reservoir formation. Furthermoreleaking longitudinal gaps may be formed between the various cells of thecellular tube, which gaps will reduce the equalization of the fluidinjection into formation layers with different permeabilities.

[0015] It is also observed that conventional sandscreens may becomeplugged with fines that are trapped within the screen. However, in suchcase the fines are decreasing the permeability of the sieve openings ofthe screen, whereas the permeability of the screen itself will remain afew thousand Darcy.

DESCRIPTION OF A PREFERRED EMBODIMENT

[0016] The invention will be explained in more detail with reference toFIG. 1, which shows a well traversing a stratified reservoir formation.

[0017] The well 1 extends from fluid processing facilities 2 at theearth surface 3 into a stratified subsurface reservoir formation 4.

[0018] The four strata 4A-D of the formation 4 each have differentpermeabilities. Strata 4B and 4D may be oil-bearing strata having arelatively low permeability of for example less than 10 Darcy.

[0019] Stratum 4A may be gas-bearing and stratum 4C may be water-bearingand these strata may have a permeability of for example between 10 and50 Darcy.

[0020] The fluid inflow zone of the well 1 is equipped with a welllining 5 having a lower permeability than the gas- and water-bearingstrata 4A and 4C. As a result of the low permeability of the lining 5,which in the example shown will be selected somewhere between 1 and 50Darcy, the variation of influx from the different strata 4A-4D isreduced.

[0021] In order to counteract production losses as a result of the lowpermeability of the lining 5 a downhole pump 6 may be installed in thewell.

[0022] If steam, acid or another production stimulation or treatmentfluid is to be injected through the lining 5 into the formation 4 thenthe low permeability of the lining 5 will equalize the fluid injectionrate into various strata 4A-4D so that fluid losses into the mostpermeable strata 4A and 4 are reduced and an effective stimulation ortreatment of the oil-bearing strata 4B and 4D is established.

[0023] If the formation 4 is fractured or contains cavities the lining 5will also equalize the fluid injection rate into the various strata4A-4D so that fluid losses into the fracture or cavities are reduced andan effective stimulation or treatment of the oil-bearing strata 4B and4D is established. In such case the very high permeability of thefracture or cavity will be ignored and the permeability of the lining 5will be selected lower than the permeability of the most permeableunfractured stratum 4A-4D, which will be less than 50 Darcy.

[0024] The method according to the invention is not only useful forestablishing an equal fluid transfer between an oil or gas production orfluid injection well and a subsurface oil and/or gas bearing formationbut is also useful for injecting treatment fluids equally from aclean-up well into a formation which is polluted with chemicals and toextract these chemicals from the polluted formation in an equal manneralong the length of the clean-up well.

1. A method of transferring fluid between a subsurface formation andfluid processing facilities at or near the earth surface via a wellextending between said subsurface formation and fluid processingfacilities, wherein the fluid is transferred via a permeable welllining, which has a permeability of less than 50 Darcy.
 2. The method ofclaim 1, wherein the well lining has a lower permeability than at leastpart of the subsurface formation in the vicinity of the well lining. 3.The method of claim 1, wherein the well traverses several zones of asubsurface reservoir formation, which zones have differentpermeabilities and the permeability of the well lining is selected lowerthan the permeability of the zone having the highest permeability. 4.The method of claim 1, wherein the permeability of the well lining isless than 10 Darcy.
 5. The method of claim 1, wherein the well lining isunfolded and/or expanded downhole and pressed against the wall of thewellbore or perforated production liner either by mechanical force or byhydraulic pressure and is made of a low permeable screen material suchas a fabric, permeable rubber, a woven or sintered screen or a laserpunched plate.
 6. The method of claim 5, wherein the well lining isformed by an expandable hose or bladder, which is pressed against thewall of the wellbore either by mechanical force or by hydraulic pressurein case fluid is injected from the well into the formation.
 7. Themethod of claim 5, wherein the well lining is pressed against the wallof the borehole or a perforated production liner by an expandableslotted or otherwise perforated tubular or by a perforated corrugated,cellular, or foldable tubular which is brought into a tubular shapedownhole.
 8. The method of claim 5, wherein the well lining is formed byan expandable perforated tubular or by a corrugated or foldable tubularwhich is brought into a tubular shape downhole.
 9. The method of claim1, wherein fluid, such as steam, gel, surfactant, resin, one- ortwo-component cement, or another treatment or stimulation fluid, ispumped from said fluid processing facilities via the well and welllining into the reservoir formation.
 10. The method of claim 1, whereinthe fluid comprises a hydrocarbon fluid, which flows from a subsurfacereservoir formation via the well lining and well towards hydrocarbonfluid processing facilities at or near the earth surface.
 11. The methodof claims 1, 9 and 10, wherein the steps of claims 9 and 10 arealternated.